The knee joint is a largest, complex synovial joint of a modified hinge variety. There are three articulations. in the knee joint i.e. two between the tibial and femoral condyles and the third with the patella and femur. The main movements occurring on it are flexion and extension on a horizontal axis; but in addition it displays some degree of rotatory movement called locking and unlocking on a vertical axis. It is mainly weight bearing but also helps in locomotion. Man has evolved and has got erect posture and hence advantage of standing on two legs which means weight of the upper part of the body needs to be balanced and carried by the lower limbs. Knee joint along with other structures carries and bears the body weight. This can produce adverse effects on the joint which is subjected to constant stress and thus undergoes wear and tear. This disturbs the homeostasis of the knee joint. Understanding the normal structural organization and functional homeostatic limits is necessary to predict the disease of knee joint.

Introduction and Aim: Knee Osteoarthritis (KOA) is a common degenerative joint disease which is one of the leading causes of disability in elderly people. Electromyography (EMG) is an electrophysiological method in evaluating skeletal muscle activity. Low-level laser (light) therapy (LLLT) is a modality of treatment used in several conditions required to suppress the pain, inflammation, stimulation of healing and restoration of function. Surface EMG parameters were studied before and after the low level laser therapy in subjects with knee osteoarthritis.  Materials and Methods: Subjects with knee OA participated in the study. Low level laser therapy (LLLT) was administered using a laser device with probe giving maximum power output of 10 mw with a wavelength of 810 nm. Surface electromyography (sEMG) of quadriceps muscles was recorded in all the study participants before and after the therapy. The parameters were statistically compared.  Results: There was a statistically significant difference between the maximum contraction and duration of contraction before and after the laser intervention in all the muscles.  Conclusion: It can be concluded that the muscle performance increased in the subjects with knee OA after the LLLT.